Subgun finishing question

Is it necessary to blue or otherwise finish the inside of a tube type receiver? Some of these sub gun semi builds are beginning to come together and I was just curious whether it was necessary.

Looking at the cut receiver pieces it looks like they were blued but I wonder if something like guncote would be better to use since they are semi auto or would a cold blue be fine with a guncote finish on the outside. I tend towards the latter when I get to the build. Cold blue the inside and paint the outside. Anybody know?

I was going to blast with aluminum oxide and use kphos as the prep on the exterior and just either blue or kphos the inside, probably the latter. I am planning to use the Teflon/moly Oven Cure I got from Brownell on the exterior. I ordered that thinking I would use it on an AK. Would that work on the inside of the tube as well?

My experience with guncote to date has been outstanding and makes everything very easy to clean and maintain.

I was being a bit facitious , sorry . Overspray is just what ends up in the tube from painting the outside . I never bother with the inside of a tube gun , never have any problems with rust , oil in there and whatnot . Can't see where blueing would hurt , or even actually getting a coat of Guncoat in there . I just keep the inside oiled and never worried about it .

That answers my question, and demonstrates a little ignorance as well, I should have picked that up. I think I will just do the prep and spray the outside when I am finally that far along which hopefully won't be too long. This project has taken a while. I hope it is worth it. These semi conversions are not easy to do and stay within the law. Quite a challenge and I hope it works.